Conventionally, an imaging device such as a camera has an image pickup optical system composed of a plurality of lenses and image sensors such as charge coupled devices (CCDs) placed at specified positions, in which arrangement a subject image to be formed based on a light pencil incident on the image pickup optical system is formed by the image sensors.
In this type of imaging device, for autofocus function and zoom function, a lens driving device for moving the lens in an optical axis direction is used. In this lens driving device, generally, by rotating a lead screw with use of a stepping motor or the like as a driving source, a lens holding frame is moved in the optical axis direction via a nut having a female screw portion engaged with the lead screw.
In such a lens driving device, the lens holding frame and the nut are fitted to each other, or thrust into contact (urged) against each other with aid of a reaction force (preload) of a spring material, so as to allow individual components involved to smoothly operate, by which backlashes that occur to the lens holding frame in the optical axis direction (thrust direction) are absorbed.
Also in an orthogonal direction (radial direction) that orthogonally intersects the optical axis direction, there occur backlashes due to clearances of components between the guide shaft and the bearing of the lens holding frame, as well as between the lead screw and the nut. Therefore, another spring material is used to apply the urgency in the radial direction as well (JP 2000-206391 A).
On the other hand, there has been known an imaging device in which a mechanical shutter for adjusting light quantity in response to the brightness of the subject is fixed to a lens holding frame so that the mechanical shutter is moved integrally with the lens holding frame (JP H5-134159 A).
In such an imaging device, a flexible printed circuit (FPC) board for controlling the opening and closing of the mechanical shutter changes in configuration along with the movement of the lens holding frame, causing a reaction force of the configuration change to act on the lens holding frame.